Field of the Invention
The invention relates generally to downhole tools for use in wells, and more particularly to means for securing coils of magnet wire in the stator of a linear motor.
Related Art
In the production of oil from wells, it is often necessary to use an artificial lift system to maintain the flow of oil. The artificial lift system commonly includes an electric submersible pump (ESP) that is positioned downhole in a producing region of the well. The ESP has a motor that receives electrical signals from equipment at the surface of the well. The received signals run the motor, which in turn drives a pump to lift the oil out of the well.
ESP motors may use rotary designs in which a rotor is coaxially positioned within a stator and rotates within the stator, or linear designs in which a mover moves in a linear, reciprocating motion, driving a plunger-type pump to force oil out of the well. Both rotary and linear motors use coils of magnet wire that are energized to create magnetic fields. These magnetic fields interact with magnetic fields of the motor's rotor (in the case of a rotary motor) or mover (in the case of a linear motor), thereby causing the rotor or mover to move. This movement is used to drive the system's pump.
In the case of rotary motors, the coils are typically positioned in axially oriented slots in a stator core, and are thereby prevented from moving as they cause the rotor to rotate. In the case of linear motors, the coils are commonly wrapped annularly around the bore of the stator, so the reactive force on the coils as they drive the mover to reciprocate may cause the coils to move axially. This movement may result in abrasion of the wires and may lead to short circuits or other electrical failures of the coils.
It would therefore be desirable to provide improved means to reduce or prevent the movement of the coils in a linear motor, thereby increasing the reliability and working life of the motor.